Class RadialGradientPaint

The RadialGradientPaint class provides a way to fill a shape with
a circular radial color gradient pattern. The user may specify 2 or more
gradient colors, and this paint will provide an interpolation between
each color.

The user must specify the circle controlling the gradient pattern,
which is described by a center point and a radius. The user can also
specify a separate focus point within that circle, which controls the
location of the first color of the gradient. By default the focus is
set to be the center of the circle.

This paint will map the first color of the gradient to the focus point,
and the last color to the perimeter of the circle, interpolating
smoothly for any in-between colors specified by the user. Any line drawn
from the focus point to the circumference will thus span all the gradient
colors.

Specifying a focus point outside of the radius of the circle will cause
the rings of the gradient pattern to be centered on the point just inside
the edge of the circle in the direction of the focus point.
The rendering will internally use this modified location as if it were
the specified focus point.

The user must provide an array of floats specifying how to distribute the
colors along the gradient. These values should range from 0.0 to 1.0 and
act like keyframes along the gradient (they mark where the gradient should
be exactly a particular color).

In the event that the user does not set the first keyframe value equal
to 0 and/or the last keyframe value equal to 1, keyframes will be created
at these positions and the first and last colors will be replicated there.
So, if a user specifies the following arrays to construct a gradient:

{Color.BLUE, Color.RED}, {.3f, .7f}

this will be converted to a gradient with the following keyframes:

{Color.BLUE, Color.BLUE, Color.RED, Color.RED}, {0f, .3f, .7f, 1f}

The user may also select what action the RadialGradientPaint object
takes when it is filling the space outside the circle's radius by
setting CycleMethod to either REFLECTION or REPEAT.
The gradient color proportions are equal for any particular line drawn
from the focus point. The following figure shows that the distance AB
is equal to the distance BC, and the distance AD is equal to the distance DE.

If the gradient and graphics rendering transforms are uniformly scaled and
the user sets the focus so that it coincides with the center of the circle,
the gradient color proportions are equal for any line drawn from the center.
The following figure shows the distances AB, BC, AD, and DE. They are all equal.

Note that some minor variations in distances may occur due to sampling at
the granularity of a pixel.
If no cycle method is specified, NO_CYCLE will be chosen by
default, which means the the last keyframe color will be used to fill the
remaining area.

The colorSpace parameter allows the user to specify in which colorspace
the interpolation should be performed, default sRGB or linearized RGB.

The following code demonstrates typical usage of
RadialGradientPaint, where the center and focus points are
the same:

IllegalArgumentException - if radius is non-positive,
or fractions.length != colors.length,
or colors is less than 2 in size,
or a fractions value is less than 0.0 or greater than 1.0,
or the fractions are not provided in strictly increasing order

IllegalArgumentException - if radius is non-positive,
or fractions.length != colors.length,
or colors is less than 2 in size,
or a fractions value is less than 0.0 or greater than 1.0,
or the fractions are not provided in strictly increasing order

IllegalArgumentException - if radius is non-positive,
or fractions.length != colors.length,
or colors is less than 2 in size,
or a fractions value is less than 0.0 or greater than 1.0,
or the fractions are not provided in strictly increasing order

RadialGradientPaint

Constructs a RadialGradientPaint with a default
SRGB color space, using the center as the focus point.

Parameters:

center - the center point, in user space, of the circle defining
the gradient

radius - the radius of the circle defining the extents of the
color gradient

fractions - numbers ranging from 0.0 to 1.0 specifying the
distribution of colors along the gradient

colors - array of colors to use in the gradient. The first color
is used at the focus point, the last color around the
perimeter of the circle.

cycleMethod - either NO_CYCLE, REFLECT,
or REPEAT

Throws:

NullPointerException - if center point is null,
or fractions array is null,
or colors array is null,
or cycleMethod is null

IllegalArgumentException - if radius is non-positive,
or fractions.length != colors.length,
or colors is less than 2 in size,
or a fractions value is less than 0.0 or greater than 1.0,
or the fractions are not provided in strictly increasing order

IllegalArgumentException - if radius is non-positive,
or fractions.length != colors.length,
or colors is less than 2 in size,
or a fractions value is less than 0.0 or greater than 1.0,
or the fractions are not provided in strictly increasing order

center - the center point, in user space, of the circle defining
the gradient. The last color of the gradient is mapped
to the perimeter of this circle.

radius - the radius of the circle defining the extents of the color
gradient

focus - the point in user space to which the first color is mapped

fractions - numbers ranging from 0.0 to 1.0 specifying the
distribution of colors along the gradient

colors - array of colors to use in the gradient. The first color
is used at the focus point, the last color around the
perimeter of the circle.

cycleMethod - either NO_CYCLE, REFLECT,
or REPEAT

Throws:

NullPointerException - if one of the points is null,
or fractions array is null,
or colors array is null,
or cycleMethod is null

IllegalArgumentException - if radius is non-positive,
or fractions.length != colors.length,
or colors is less than 2 in size,
or a fractions value is less than 0.0 or greater than 1.0,
or the fractions are not provided in strictly increasing order

center - the center point in user space of the circle defining the
gradient. The last color of the gradient is mapped to
the perimeter of this circle.

radius - the radius of the circle defining the extents of the
color gradient

focus - the point in user space to which the first color is mapped

fractions - numbers ranging from 0.0 to 1.0 specifying the
distribution of colors along the gradient

colors - array of colors to use in the gradient. The first color
is used at the focus point, the last color around the
perimeter of the circle.

cycleMethod - either NO_CYCLE, REFLECT,
or REPEAT

colorSpace - which color space to use for interpolation,
either SRGB or LINEAR_RGB

gradientTransform - transform to apply to the gradient

Throws:

NullPointerException - if one of the points is null,
or fractions array is null,
or colors array is null,
or cycleMethod is null,
or colorSpace is null,
or gradientTransform is null

IllegalArgumentException - if radius is non-positive,
or fractions.length != colors.length,
or colors is less than 2 in size,
or a fractions value is less than 0.0 or greater than 1.0,
or the fractions are not provided in strictly increasing order

gradientBounds - the bounding box, in user space, of the circle
defining the outermost extent of the gradient

fractions - numbers ranging from 0.0 to 1.0 specifying the
distribution of colors along the gradient

colors - array of colors to use in the gradient. The first color
is used at the focus point, the last color around the
perimeter of the circle.

cycleMethod - either NO_CYCLE, REFLECT,
or REPEAT

Throws:

NullPointerException - if gradientBounds is null,
or fractions array is null,
or colors array is null,
or cycleMethod is null

IllegalArgumentException - if gradientBounds is empty,
or fractions.length != colors.length,
or colors is less than 2 in size,
or a fractions value is less than 0.0 or greater than 1.0,
or the fractions are not provided in strictly increasing order

getCenterPoint

getFocusPoint

Returns a copy of the focus point of the radial gradient.
Note that if the focus point specified when the radial gradient
was constructed lies outside of the radius of the circle, this
method will still return the original focus point even though
the rendering may center the rings of color on a different
point that lies inside the radius.